Interface-engineered γ/α-hematite homojunction with low contact barrier for boosted photocatalytic peroxymonosulfate activation.

Although iron oxide-based catalysts have drawn much attention as eco-friendly materials for photocatalytic peroxymonosulfate (PMS) activation, their catalytic activity remains constrained by inefficient charge separation. Herein, a γ/α-phase hematite (Fe2O3) homojunction with a low contact barrier was developed, which showed efficient photogenerated charge separation and very highly catalytic activity for PMS activation under light irradiation. The optimized γ/α-phase hematite homojunction (γ/α-500) catalyst activating PMS achieved a superior metronidazole degradation rate of 0.021 min-1 under light irradiation, which was 1.90 and 2.63 times higher than those of single-phase γ-Fe2O3 and α-Fe2O3, respectively. Beyond high activity, γ/α-500 maintained robust performance across a wide pH window (3-11), showed strong tolerance toward anion interference, and delivered stable reusability. Characterizations and theory calculations indicate that the homojunction-induced built-in electric field greatly facilitated charge separation, and enhanced PMS adsorption and reduced activation energy. This work not only demonstrates the design of a γ/α-phase Fe2O3 homojunction with an ultralow energy barrier for PMS activation but also offers a promising strategy for tailoring iron oxide-based catalysts toward efficient and sustainable remediation of emerging contaminants.